1. Field of the Invention
The present invention generally relates to the storage of fissile materials and, in particular, to systems and methods for storing fissile materials that utilize coatings formed, at least in part, of neutron-absorbing materials.
2. Description of the Related Art
Fissile materials (materials capable of fissioning), although providing significant benefits, inherently suffer from problems associated with their storage, such as storage that is utilized after a useful life of the fissile material has expired. For instance, nuclear fuel discharged from fission reactors, referred to hereinafter as Spent Nuclear Fuel (SNF), typically is stored in deep pools filled with water, with the water being provided to dissipate heat and to attenuate gamma and neutron radiation generated by the SNF. As an alternative to storing SNF in water-filled pools (xe2x80x9cwet storagexe2x80x9d), xe2x80x9cdry storagexe2x80x9d techniques also have been utilized.
In a typical dry-storage application, the SNF is stored in a substantially horizontal or substantially vertical configuration within a protective vessel which, typically, includes a heavy-walled structure, and which typically is referred to as the xe2x80x9ccaskxe2x80x9d or xe2x80x9coverpack.xe2x80x9d Heretofore, such wet and dry-storage techniques of SNF have been widely viewed as commercially viable radioactive material storage options possessing characteristics for enabling economical long-term storage.
As is known, one of the most important aspects of storing SNF is the control of neutron multiplication so as to prevent a self-sustaining chain reaction within the stored SNF. Such a self-sustaining chain reaction is known as xe2x80x9cachieving criticalityxe2x80x9d or becoming xe2x80x9ccritical.xe2x80x9d Controlling neutron multiplication within the SNF (a process commonly referred to as xe2x80x9ccriticality controlxe2x80x9d) typically is accomplished by providing a material between and/or among individual SNF assemblies for absorbing thermalized neutrons and preventing the neutrons from causing fission events in the SNF. Such a material, commonly referred to as a xe2x80x9cneutron absorber,xe2x80x9d xe2x80x9cneutron-absorbing materialxe2x80x9d or xe2x80x9cneutron poison,xe2x80x9d typically is mechanically fastened to or mixed with the material, i.e., metal, of the structures which form the boxes or other containers for holding the SNF assemblies.
Typically, neutron absorbers or poisons contain an isotope, such as Boron-10, that absorbs neutrons. These isotopes typically are provided as part of another chemical compound, such as boron carbide (B4C), for example. The chemical compound, e.g., B4C, usually is mixed with yet another material, e.g., a metal, such as aluminum, for example, and is formed into plates. The plates are then mechanically fastened to the structures containing the SNF. Another approach has been to mix the chemical compound with the material which forms the structures for containing the SNF, and then forming the structures with the combined material. As is known, utilization of either of these aforementioned approaches tends to provide an isotope for capturing thermalized neutrons that is significantly diluted by other materials, thereby reducing the potential effectiveness of the isotopes. Additionally, the procedures utilized for attaching the materials containing the poisons to, or mixing the chemical compound containing the poisons with, the structural material may involve undesirable material limitations and/or associated costs.
Therefore, there is a need for improved systems and methods which address these and other shortcomings of the prior art.
Briefly described, the present invention relates to the storage of fissile materials and, in some embodiments, to the storage of spent nuclear fuel (SNF). In a preferred embodiment, the present invention may generally be construed as providing a method for storing fissile materials and includes the steps of: providing a storage container configured to receive the fissile materials therein, and; applying a coating to a surface of the storage container. Preferably, the coating is formed, at least in part, of a neutron-absorbing material which may be adapted to reduce neutron multiplication of the fissile material received within the storage container.
An alternative method includes the steps of: providing a storage container configured to receive fissile material therein; applying a coating to a surface of the storage container, the coating being formed, at least in part, of a neutron-absorbing material; and arranging a neutron-thermalizing medium proximate to the coating so that the coating and the neutron-thermalizing medium cooperate to form a shielding about at least a portion of the fissile material received within the storage container.
In another embodiment, a system for storing SNF is provided. Preferably, the system includes a storage container configured to receive SNF therein, and a coating arranged proximate to a surface of the storage container, with the coating incorporating neutron-absorbing material.
In another embodiment, a system for storing SNF incorporates a storage container and means for absorbing neutrons arranged proximate to a surface of the storage container.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such features and advantages be included herein within the scope of the present invention, as defined in the appended claims.